Selectively refreshing address registration information

ABSTRACT

Facilitating communications within a processing environment. Inbound traffic and outbound traffic on one or more virtual interfaces of the processing environment are monitored for a predefined amount of time. Based on the monitoring, a determination is made as to whether for a selected component of a virtual interface of the one or more virtual interfaces an inbound frame has been received but an outbound frame has not been transmitted for the predetermined amount of time. Based on determining that the inbound frame has been received but the outbound frame has not been transmitted, a generated outbound frame is forwarded to cause address registration information for the virtual interface to be refreshed.

BACKGROUND

One aspect relates, in general, to network communications, and inparticular, to the refreshing of address registration information usedin communicating within a network.

Networks, such as Ethernet networks, maintain routing tables tofacilitate routing of frames within the network. One example of arouting table is a Media Access Control (MAC) forwarding table thatincludes MAC addresses used in routing frames within the network. Thesize of this table varies depending on the size and cost of the physicalswitch. With the increase in size of Layer 2 Networks in customer datacenters, due to the convergence of the 10/100 networks into the 1G/10Gnetworks, the possibility of a MAC forwarding table becoming full hasdramatically increased. To help keep the MAC forwarding tables filledwith only “active” MAC entries, many switch vendors have adopted a fiveminute MAC timeout value. This means if a switch port does not receive apacket with a source MAC address which is currently active in the MACforwarding table over the five minute interval, this MAC address ispurged from the forwarding table.

Once the MAC address is purged from the forwarding table, all packetsreceived with a destination MAC address, which is not present in the MACforwarding table, is broadcast/forwarded to all switch ports associatedwith the port group. This can cause significant switch and networkperformance issues depending on the overall Local Area Network (LAN)utilization.

BRIEF SUMMARY

Shortcomings of the prior art are overcome and additional advantages areprovided through the provision of a computer program product forfacilitating communications within a processing environment. Thecomputer program product includes a computer readable storage mediumreadable by a processing circuit and storing instructions for executionby the processing circuit for performing a method. The method includes,for instance, monitoring, for a predefined amount of time, inboundtraffic and outbound traffic on a virtual interface of the processingenvironment; determining based on the monitoring whether for a selectedcomponent of the virtual interface an inbound frame has been receivedbut an outbound frame has not been transmitted for the predefined amountof time; and based on determining that the inbound frame has beenreceived but the outbound frame has not been transmitted, forwarding agenerated outbound frame to cause address registration information forthe virtual interface to be refreshed.

Methods and systems relating to one or more aspects are also describedand claimed herein. Further, services relating to one or more aspectsare also described and may be claimed herein.

Additional features and advantages are realized through the techniquesdescribed herein. Other embodiments and aspects are described in detailherein and are considered a part of the claimed aspects.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

One or more aspects are particularly pointed out and distinctly claimedas examples in the claims at the conclusion of the specification. Theforegoing and objects, features, and advantages of one or more aspectsare apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts one embodiment of a processing environment to incorporateand use one or more aspects of a monitoring and refresh capability;

FIG. 2A depicts one example of a connection id table including countersto be used in monitoring;

FIG. 2B depicts one example of a MAC address routing table includingcounters to be used in monitoring;

FIG. 2C depicts one example of a monitoring queue;

FIG. 3 depicts one embodiment of initialization performed to support themonitoring and refresh capability of one aspect;

FIGS. 4A-4C depict an example of a format of a refresh primitive;

FIG. 5 depicts one embodiment of the logic to monitor inbound/outboundtraffic and to selectively refresh address registration information;

FIG. 6 depicts one example of updating inbound counters;

FIG. 7 depicts one example of updating outbound counters; and

FIG. 8 depicts one embodiment of a computer program productincorporating one or more aspects.

DETAILED DESCRIPTION

In one aspect, communications within a processing environment arefacilitated by refreshing address registration information used in thecommunications. The address registration information is used to forwardframes within the environment, and is maintained in a data structure,such as a routing table. Since the data structure is of a finite size,addresses within the data structure that have not been used in apredefined amount of time are removed from the data structure. Once anaddress is removed, if a frame arrives destined for that address, theframe is broadcast to a plurality of destinations, instead of the oneparticular destination, until the address is re-registered. Therefore,in accordance with one aspect, a monitoring capability is provided thatmonitors network interfaces of the environment for inbound and outboundtraffic and takes action if it is determined that for a specified periodof time there has been inbound traffic, but no outbound traffic, for aparticular interface. The action taken includes refreshing the addressregistration information for the interface to enable the incoming framesto be forwarded to a particular destination, as intended, rather thanbroadcast to the plurality of destinations.

In a further embodiment, the monitoring capability monitors particularaddresses of one or more interfaces for inbound and outbound traffic andtakes action if it is determined for a specified period of time thatthere has been inbound traffic, but no outbound traffic, for aparticular address. Again, the action includes refreshing the addressregistration information for the interface corresponding to the address.

One embodiment of a processing environment to incorporate and use one ormore aspects of the monitoring/refresh capability is described withreference to FIG. 1. In one example, a processing environment 100 isbased, for instance, on the z/Architecture offered by InternationalBusiness Machines Corporation, Armonk, New York, and includes, forinstance, a zSeries server, also offered by International BusinessMachines Corporation. The z/Architecture is described in a publicationentitled “z/Architecture—Principles of Operation,” IBM® Publication No.SA22-7832-09, Tenth Edition, September 2012, which is herebyincorporated herein by reference in its entirety. Z/ARCHITECTURE®,ZSERIES®, and IBM® are registered trademarks of International BusinessMachines Corporation, Armonk, N.Y., U.S.A. Other names used herein maybe registered trademarks, trademarks or product names of InternationalBusiness Machines Corporation or other companies.

In one example, processing environment 100 includes a central processorcomplex (CPC) 102, having, for instance, one or more partitions or zones104 (e.g., logical partitions LPAR L1-LPAR L3). Each logical partitionhas a resident operating system 106, which may differ for one or more ofthe logical partitions. For example, logical partition 1 includes thez/OS operating system, offered by International Business MachinesCorporation; logical partition 2 is executing a z/VM operating system,offered by International Business Machines Corporation; and logicalpartition 3 is operating an enhanced z/VM operating system. Although inthis example, three logical partitions are described, other embodimentscan include more, less or the same number of logical partitions.Further, one or more of the partitions may not be executing an operatingsystem, and/or operating systems other than those described herein maybe executed. Many other variations are possible. Z/OS® and Z/VM® areregistered trademarks of International Business Machines Corporation.

Each logical partition includes one or more logical processors, each ofwhich represents all or a share of a physical processor of theprocessing environment allocated to the partition. The logicalprocessors of a particular partition may be either dedicated to thepartition so that the underlying processor resource is reserved for thepartition, or shared with another partition so that the underlyingprocessor resource is potentially available to another partition.

In one embodiment, each logical partition is coupled to a shared networkconnection, such as an Open Systems Adapter Express (OSA-E) adapter 110.Adapter 110 includes, for instance, a network interface card 112(a.k.a., a physical interface), at least one processor (e.g., centralprocessing unit (CPU)) 150 and memory 152, each of which is described infurther detail below.

Network interface card 112 is the physical interface between the adapterand the logical partitions, and has associated therewith a plurality ofvirtual interfaces (a.k.a., network interfaces) 118. In one embodiment,each logical partition has one or more virtual interfaces correspondingthereto. For instance, a virtual interface 118 a corresponds to a host,such as TCPIPz1 122 a, executed by the z/OS operating system executingin LPAR1; a virtual interface 118 b corresponds to a host, such as guestC1 122 b, executing in LPAR 2; a virtual interface 118 c corresponds toa host, such as guest C2 122 c, executing in LPAR 2; and a virtualinterface 118 d corresponds to a virtual switch 124 of the z/VM VMEoperating system, executing within LPAR 3.

In one implementation, each virtual interface is coupled to a devicewithin a logical partition. For instance, virtual interface 118 a iscoupled to a device 120 a in LPAR 1; virtual interfaces 118 b, 118 c arecoupled to devices 120 b, 120 c, respectively, in LPAR 2; and virtualinterface 118 d is coupled to a device 120 d in LPAR 3. In turn, device120 a is further coupled to TCPIPz1 122 a in LPAR 1; devices 120 b, 120c are further coupled to Guest C1 122 b, Guest C2 122 c, respectively,in LPAR 2; and device 120 d is further coupled to virtual switch 124 inLPAR 3.

Virtual switch 124 enables further sharing of data among Guest E1 126 a,Guest E2 126 b and Guest E3 126 c of LPAR 3. The virtual switch includesa plurality of ports 128 a, 128 b and 128 c, each of which is coupled toa respective guest via a virtual network interface 130 a, 130 b, and 130c, respectively. The virtual switch allows the guests coupled thereto tocommunicate with one another without using the adapter or an externalnetwork.

Network interface card 112 is coupled to an external network 114 via aport 116. Network 114 includes one or more switches 117 and is used tocommunicate between the logical partitions of this processingenvironment and/or with processors of other processing environments. Theswitch directly coupled to port 116 is referred to as the nearestneighbor switch.

In one example, each switch (or a subset thereof) includes a routingdata structure 140, such as a MAC forwarding table, that includesaddress registration information used in forwarding frames within theprocessing environment, and a refresh timer 142 (e.g., a MAC refreshtimer) that is used to purge the non-accessed entries of the table. Inone particular example, in which the network is an Ethernet network, theaddress registration information includes one or more Media AccessControl (MAC) addresses assigned to one or more virtual interfaces ofthe physical interface.

Returning to adapter 110, processor 150 executes, in accordance with oneaspect, a monitor facility 154 that monitors traffic on the virtualinterfaces of the processing environment, and selectively refreshes theaddress registration information, based on the monitoring, asappropriate. The monitoring facility uses information stored in memory152, including, for instance, one or more of a connection id table 156,an address table 158 (a.k.a., an address routing table), a monitoringqueue 160, and a global indicator 162 to determine whether the addressregistration information is to be selectively refreshed.

In one embodiment, referring to FIG. 2A, a connection id table 156includes one or more entries 200, and each entry corresponds to aparticular virtual interface. Each entry 200 includes, for instance, aconnection identifier (ID) 202 assigned to a particular virtualinterface to identify that interface; an indication of the virtualinterface 204 owned by the connection id; a set of inbound/outboundcounters 206 associated with the connection id for tracking incoming andoutgoing frames, respectively, for the virtual interface; and a scopeindication 208 that indicates whether the virtual interface, as oneentity, is being monitored (referred to as interface scope, in whichtraffic associated with a connection identifier assigned to the virtualinterface is being monitored), or whether a particular address of theinterface is being monitored (referred to as address scope).

Referring to FIG. 2B, in one embodiment, address table 158, such as aMAC address routing table, also includes a plurality of entries 250.However, for this table, each entry 250 includes, for instance, anaddress 252, such as a MAC address; a set of inbound/outbound counters254 for tracking incoming and outgoing frames, respectively, for theaddress; and an owner indication 256 that is, for instance, theconnection identifier owning this address. This connection identifier isused as an index into the connection id table to obtain the connectionid entry that owns this address.

As one example, the connection id table includes up to 1920 entries andthe MAC address routing table includes up to 4096 entries. However, inother embodiments, other numbers of entries may be included in eachtable. In one example, the more memory that is available, the greaterthe number of entries may be included.

Entries are included within the connection id table and MAC addresstable based on, for instance, creation of a host virtual machine and/orbased on an indication that monitoring is to be performed for thevirtual interfaces represented in the tables. This indication isprovided by, for instance, a refresh primitive, described below, or by aglobal indicator 162 (FIG. 1). In one implementation, global indicator162 indicates whether or not monitoring is to be performed for thevirtual interfaces of the processing environment. Further, if monitoringis to be performed, a thread sleep value is provided that indicates atwhat time interval the monitoring is to be performed. The globalindicator is set by a System Network Administrator, or automaticallybased, for instance on, heuristics, and is not to be overridden byindividual interfaces. In a further embodiment, the global indicator isnot provided.

In addition to the above, monitoring queue 160 is provided that includesentries, from either the connection id table or address table, to bemonitored. The entries are provided on the monitoring queue based onreceiving refresh primitives indicating the entries are to be monitoredor based on the global indicator specifying monitoring. In one example,as shown in FIG. 2C, monitoring queue 160 includes a plurality ofentries 270, and each entry includes, for instance, a pointer 272 to aparticular table entry of a specified type (e.g., connection id tableentry or MAC address routing table entry) depending on the scope ofmonitoring. The type of entry pointed to by pointer 272 indicates themonitoring scope (e.g., interface or address), or in another embodiment,a separate indicator is included in the queue entry that specifies themonitoring scope. Other variations are also possible.

Further, in one embodiment, each entry 270 includes a refresh eventindicator 274 that indicates whether a refresh frame has been sent forthis entry to refresh the address registration information in the switchforwarding table. This indicator is used, in one embodiment, to controlwhen the counters associated with the entry are to be checked.

Although examples of data structures (e.g., tables) are shown anddescribed, other examples are possible. Each data structure may beformatted in other ways and/or include additional, less and/or differentinformation. Further, a data structure may include a plurality of datastructures coupled to one another. Many variations are possible.

As described herein, since the routing data structures in the switchesare of a finite size, not all addresses are included in the datastructures. For instance, in an Ethernet network, each Ethernet switchmaintains a MAC forwarding table. The size of this table variesdepending on the size and cost of the physical switch. With the increasein size of Layer 2 Networks in customer data centers, the possibility ofthese MAC forwarding tables becoming full has dramatically increased. Tohelp keep the MAC forwarding tables filled with only “active” MACentries, many switch vendors have adopted a MAC timeout value (a.k.a., aMAC refresh value), such as a five minute interval. This interval isreduced from previous values because of the increase in the size of theLayer 2 Networks. This means if a switch port does not receive a packetwith a source MAC address which is currently active in the MACforwarding table over the specified interval, this MAC address is purgedfrom the forwarding table.

Once the MAC address is purged from the forwarding table, all packetsreceived with a destination MAC address which is not present in the MACforwarding table will be broadcast/forwarded to all switch portsassociated with the port group. This can cause significant switch andnetwork performance issues depending on the overall LAN utilization.

This is problematic for applications, like Sysplex Distributor (SD) andWorkload Balancers/Managers (WLM) executed by the operating system,which receive inbound traffic flows on one virtual interface, but sendoutbound traffic flows on a different interface (e.g., of a differentLPAR). Typically, SD and WLM interfaces only send packets outbound onthe interface on the SYS/SYN ACK/ACK flow to setup a new connection.After this setup completes, subsequent packets are processed by adifferent host. The outbound packets are sent with a source MAC addressof the responding interface. In many instances, no outbound flows withthe source MAC address of the SD or WLM host (e.g., TCPIP) will occuruntil a new connection is established.

When Sysplex Distributor and Workload Manager interfaces do not have anynew connection setups, it is possible no outbound packets on theseinterfaces are generated. If no new connections are established and theMAC timeout period expires, the MAC address for that host is deletedfrom the forwarding table. The worst case scenario is when the inboundtraffic flows on one virtual interface, but the outbound traffic flowsare on a different virtual interface. In this scenario, once the MACaddress for the inbound flow is dropped by the switch, there could be alarge number of packets being flooded to all switch ports until the MACaddress is refreshed with a new connection setup.

Another troublesome example is when the Open Shortest Path First (OSPF)methodology has defined a “Lower Cost” interface which is used to sendoutbound traffic, but for WorkLoad manager, multiple inbound interfacesare typically used.

In the case where there are many virtual interfaces for a singlephysical interface, each virtual interface is assigned its own uniqueMAC address. Each virtual interface is to have its MAC addressperiodically sent outbound to the LAN to keep the MAC address “active”in the Layer 2 forwarding tables. To ensure this occurs, in one aspect,a monitoring/refresh capability is provided for virtual interfaces thatare to partake in the monitoring/refresh capability. With such acapability, special frames are generated outbound on these interfaces,based on the monitoring, to prevent a switch from broadcasting MACpackets destined for the interface to all of its switch ports due to theMAC address being deleted due to outbound inactivity.

As a further embodiment, a virtual interface may have a plurality of MACaddresses assigned thereto, and an outbound frame is sent for each orselected addresses of the interface.

In one aspect, the monitor/refresh capability includes a monitor, suchas monitor 154, used to monitor the inbound and outbound traffic onevery virtual interface (or a select subset) connected to a physical LANinterface. Over a specified time interval, the inbound and outboundpacket counts processed for the MAC address (or addresses) associatedwith the virtual interface are recorded. The time interval is set, forinstance, based on the MAC refresh timer value specified in the nearestneighbor switch (e.g., switch 117) to which the LAN adapter isconnected.

As a new host virtual machine is created, a virtual interface for thevirtual machine is added to a monitoring queue, such as monitoring queue160 maintained within memory 152 of adapter 110, if monitoring is to beperformed for the virtual interface. During initialization of theinterface, a unique MAC address and connection id are created touniquely identify the virtual interface. Further, during initialization,outbound frames are generated to cause the MAC address to be added tothe MAC Forwarding table in the switch. Additionally, in one embodiment,a connection id entry is added to connection id table 156 for thisinterface, and an address entry is added to MAC address table 158. Ifmultiple MAC addresses are created and assigned to the virtual address,then multiple entries are added to the MAC address table 158. Inboundand outbound counters are also created and included in the tables, asdescribed above.

In one example, as frames are processed for a specific virtual host onthe outbound side, the connection id is used to associate the virtualinterface of that host to its outbound frame counter associated with theconnection id. As outbound frames are sent to the LAN, the counter isincremented. Frames which are sent LPAR to LPAR and not onto the LAN donot increment the outbound counter, since these frames are not seen bythe external switch.

LAN frames processed on the inbound side use the destination MAC addressin the LAN header to determine the virtual interface. A search of theregistered MAC address is performed, and the virtual interfaceconnection id is found in the MAC address table. The inbound framecounter in, for instance, the connection id table is then incrementedfor each frame processed.

To check the counters, a thread (referred to in one example as a monitorthread or special thread) is defined in, for instance, monitor 154, andis scheduled based on the MAC refresh timer (e.g., five minutes) set inthe external switch. For instance, the thread is awoken based on a“sleep” value, which is set based on the MAC refresh timer set in theexternal switch, as described below. In one implementation, each virtualinterface specifies, via, for instance, a refresh primitive, if it wantsto participate in the MAC monitor/refresh capability and the timer onwhich the thread “sleep” value is based. This selectivity is desiredsince a virtual interface may determine its traffic flows will not fallinto any of the categories described above and the MAC refresh issuewill not occur. Thus, it does not need monitoring. In anotherimplementation, however, one global setting (e.g., global indicator 162)is used to control the thread “sleep” value, which is controlled by asingle System Network Administrator. This value is not capable of beingoverridden by a virtual interface, in one example.

Each time the monitor thread executes, it interrogates monitoring queue160. If the counters associated with an entry on the monitoring queueindicate inbound frames have been received for either the interface oraddress, depending on the type of entry being a connection id entry oraddress entry, respectively, but outbound frames have not beentransmitted, an outbound frame is generated and transmitted by themonitor thread. This frame is received by the external switch and causesaddress registration information (e.g., the virtual interface's MACaddress entry in the forwarding table) to be refreshed in the externalswitch. After the entry has been checked, the inbound and outbound framecounters are reset.

Further details regarding the monitoring/refresh capability aredescribed with reference to FIGS. 3-7. Commencing with FIG. 3, detailsare provided relating to certain initialization that occurs to performthe monitoring.

Referring to FIG. 3, in one embodiment, initially, an applicationregisters with the operating system (O/S), STEP 300. As one example, anapplication is started by a Transmission Control Protocol/InternetProtocol (TCP/IP) executed by the operating system. The operating systemknows, based on the application type, if it is an application in whichrefresh of the address registration information could be an issue, suchas with Sysplex Distributors or Workload Balancers. As examples, theoperating system makes this determination based on an application ID ofthe application or an application type parameter used when theapplication starts that describes to the operating system the type ofapplication.

In this example, the operating system determines that the application isa type of application that is to be monitored, such as SysplexDistributor or Workload Manager, STEP 302, and thus, the operatingsystem builds a refresh primitive, such as a MAC refresh primitive, toinform the monitoring logic to monitor the virtual interface associatedwith the application, STEP 304. The application may have its own MACaddress assigned thereto or it may use the MAC address for the entireconnection. If the application uses a separate MAC address, a MACrefresh primitive indicates the specific MAC address, and the scope ofthe monitoring is address scope. If not, then the MAC refresh primitiveuses the MAC address for the entire connection, and the scope of themonitoring is interface scope, STEP 306.

One example of a MAC refresh primitive is described with reference toFIG. 4A. In one example, a primitive 400 includes a command 402indicating this is a refresh monitoring command; an initiator 404indicating the initiator of the primitive (e.g., the operating systembuilding the primitive); a sequence number 406; a return code 408; a LANtype 410; a version number 412; a command count 414; Layer 2 assistssupported 416; Layer 2 assists enabled 418; a length of a subcommand420; a subcommand 422; and subcommand specific data 424.

One example of a subcommand is a start subcommand, an example of whichis depicted in FIG. 4B. The start subcommand includes, for instance, alength of the subcommand 440; the actual subcommand 442 (e.g., start);one or more flags 444 described below; a refresh timer 446 which is thevalue of the MAC refresh timer 142 (e.g., five minutes); and one or moreMAC addresses 448 that are to be monitored, if applicable. The startsubcommand starts the MAC refresh monitoring on a virtual interface or aspecific MAC address associated with the virtual interface. The flagsinclude, for instance, an interface scope in which all traffic on theinterface is applied to inbound and outbound packet counts; and a MACaddress scope in which only traffic associated with a specified MACaddress 448 (or select addresses) is applied to outbound and inboundpacket counts. The inbound and outbound packet counts are added to theMAC address entries. The MAC address is only applicable when the flagsfield is set to the MAC address scope.

Another example of a subcommand is the stop subcommand, an example ofwhich is depicted in FIG. 4C. In one example, a stop subcommand 470includes a length of the subcommand 472; the actual subcommand 474(e.g., stop); one or more flags 476; a refresh timer 478; and a MACaddress 480, if applicable. The stop subcommand disables MAC refreshmonitoring previous set with the start subcommand. In one example, theone or more flags, refresh timer and MAC address have the same values asthose in the start subcommand.

Returning to FIG. 3, the operating system sends the MAC refreshprimitive to the virtual interface, and in particular, a control planeof the virtual interface, STEP 308. The virtual interface marks eitherthe specific virtual interface or MAC address to be monitored for MACrefresh, STEP 310. The marking includes, for instance, selecting eitheran interface entry from connection id table 156 or an address entry fromaddress table 158 to be placed on the monitoring queue, depending on themonitoring scope indicated in the refresh primitive. The selected entry(i.e., an interface entry from the connection id table, if themonitoring is interface scope, or a MAC address entry from the MACaddress table, if the scope is address scope), is added to themonitoring queue, STEP 312. In particular, an entry is added to themonitoring queue, and the monitoring queue entry includes a pointer to aparticular entry in the connection id table or address table, dependingon the selected entry. The pointer implicitly indicates the type ofentry (e.g., connection id entry for interface scope, or address entryfor address scope) and/or a separate scope indicator may be included inthe queue entry.

Based on adding the entry to the monitoring queue, monitoring ofinbound/outbound traffic is performed, and the appropriate counters inthe connection id table or address routing table, based on themonitoring scope, are updated for a predefined amount of time.Thereafter, the entries on the monitoring queue are checked based on atimer event, which is based on the refresh timer value set in theprimitive. In one example, the timer event is set to a predefined amountless than the refresh timer value. If it is the first refresh entry puton the queue, then the refresh monitoring thread is started and set towake up on the timer event, STEP 314.

As a particular example, the refresh primitive is used by the operatingsystem when the application first starts, and during initializationphase, inbound and outbound traffic will flow. Once monitoring starts,the monitoring timer (e.g., thread sleep value) is set to, for instance,½ the MAC refresh timer value. Then, when a refresh event has occurredfor a monitoring queue entry (i.e., address registration information hasbeen refreshed for the queue entry), the monitoring queue entry ismarked as such in indicator 274 (e.g., indicator is set to 1). Thus, inone embodiment, this entry on the queue is now checked every other sleeptimer event. Then, based on outbound application traffic occurring forthat entry, in one embodiment, the indicator is reset (e.g., to 0), suchthat the entry is again checked at ½ the MAC refresh timer. In anotherembodiment, each entry is checked each time the thread sleep timerexpires, and the refresh event indicator is not used.

Referring to FIG. 5, when the timer (e.g., thread sleep value) expires,the counters are checked. In one embodiment, on a particular timerevent, the monitor thread of monitor 154 wakes up to check the countersassociated with entries on the monitoring queue, STEP 500. For instance,the thread interrogates an entry on the monitoring queue, STEP 502. Thisentry may be the first entry on the queue, the first entry with a setrefresh event indicator, or another selected entry, as examples. Basedon the entry type, the thread locates the counters for that entry eitherin the connection id table or the address routing table. A determinationis made as to whether the inbound counter of the entry is not equal (!=)to zero while the outbound counter is equal(==) to zero, INQUIRY 504. Ifthis evaluates to not true, then the inbound and outbound counters ofthe entry are cleared, STEP 506. Further, the next (or a selected) queueentry, if any, is obtained, STEP 508, and processing returns to INQUIRY504.

At INQUIRY 504, if the inbound counter is not equal to zero and theoutbound counter is equal to zero, then a refresh frame is generated andsent to the switch, STEP 510. The generated frame is received by theexternal switch and causes address registration information (e.g., thevirtual interface's MAC address entry in the forwarding table) to berefreshed in the external switch.

An example frame which is used is a Null Gratuitous Address ResolutionProtocol (ARP) Request frame. The contents of this specific frame are,for instance, as follows:

Destination MAC Address: FF:FF:FF:FF:FF—Broadcast

Source MAC Address: Virtual Interface MAC Address

IEEE 802.1Q VLAN Tag if defined on the Virtual Interface

Ethernet Type: 0806 (ARP)

ARP Packet Contents:

Hardware Type: 0001=>Ethernet

Protocol Type: 0800=>IP Protocol Type

Hardware Address Length: 06

Protocol Address Length: 04 (IPv4)

Opcode: 0001=>ARP Request

Source Hardware Address: Virtual Interface MAC Address

Source Protocol Address: 00000000

Destination Hardware Address: 00:00:00:00:00:00

Destination Protocol Address: 00000000

Processing then continues with STEP 506 in which the counters of theentry are cleared, and the next (or a selected) queue entry, if any, isobtained, STEP 508.

As described above, the monitoring logic checks inbound and outboundcounters and refreshes address registration information (e.g., one ormore MAC addresses) based on those counters. Thus, one embodiment of thelogic to update an inbound counter is described with reference to FIG.6. Initially, an inbound frame is received on a virtual interface, STEP600, and a search is made for the destination MAC address entry in thevirtual interface routing tables (e.g., in MAC address table 158), STEP602. Based on locating the entry, the owner field is used to extract thecorresponding host connection id entry from the connection id table,STEP 604.

Thereafter, a determination is made, based on the scope indicated in theextracted connection id entry, as to whether MAC address refreshmonitoring is active (i.e., address scope), INQUIRY 606. If addressscope monitoring is not active, then a determination is made as towhether the host connection ID entry indicates refresh monitoring isactive for the interface, INQUIRY 608. If refresh monitoring is activefor the interface (i.e., interface scope), then the inbound framecounter in the host connection ID entry is incremented, STEP 610, andthe MAC refresh code is exited, STEP 614. However, if the hostconnection ID entry indicates that the refresh monitoring for theinterface is not active, INQUIRY 608, then the refresh code is justexited, STEP 614.

Returning to INQUIRY 604, if the MAC address entry indicates MAC refreshmonitoring is active for the MAC address, then the inbound frame counterfound in the MAC address entry is incremented, STEP 612, and processingcontinues with exiting the MAC refresh code at STEP 614.

One embodiment of the logic to update an outbound counter is describedwith reference to FIG. 7. Initially, an outbound frame is received onthe virtual interface, STEP 700, and the host connection ID entryassociated with the interface on which the packet is received is locatedin the connection id table, STEP 702. A determination is made as towhether the host connection id entry indicates that interface scoperefresh is active, INQUIRY 704. If interface scope refresh is notactive, then a further determination is made as to whether the hostconnection ID entry indicates MAC address scope refresh is active,INQUIRY 706. If the MAC address scope refresh is indicated as active,then the source MAC address is extracted from the packet, and the MACaddress entry for this address is located in the MAC address table, STEP708. The outbound packet counter found in the MAC address routing tableentry is then incremented, STEP 710, and the code is exited, STEP 714.

Returning to INQUIRY 706, if the address scope MAC refresh is notactive, then the MAC refresh code is exited, STEP 714. However,returning to INQUIRY 704, if the interface scope MAC refresh indicatoris active, then the outbound frame counter in the host interface entryof the connection id table is incremented, STEP 712, and the MAC refreshcode is exited, STEP 714.

Described above is a capability of providing a traffic monitor tomonitor inbound and outbound traffic on every virtual interface (or asubset of virtual interfaces) connected to a physical LAN interface. Inone embodiment, the monitor records the inbound and outbound trafficflows processed for MAC addresses associated with a virtual interfaceover a specified interval of time based on a MAC refresh timer specifiedin the nearest neighbor switch connected to the LAN adapter.Additionally, the monitoring includes transmitting dummy outbound framesby the monitor thread for every interface to be monitored on whichinbound frames were received, but no outbound frames were transmitted.

In one embodiment, monitoring is performed, for a predefined amount oftime, of inbound traffic and outbound traffic on a virtual interface ofthe processing environment. Based on the monitoring, a determination ismade as to whether for a selected component of the virtual interface aninbound frame has been received but an outbound frame has not beentransmitted for the predefined amount of time. Based on determining thatthe inbound frame has been received but the outbound frame has not beentransmitted, a generated outbound frame is forwarded to cause addressregistration information for the virtual interface to be refreshed.

As one example, the selected component is a connection identifier inwhich all traffic on the virtual interface is monitored. In a furtherexample, the selected component is a routing address in which trafficfor that address is monitored.

In another embodiment, monitoring is performed, for a predefined amountof time, of inbound traffic and outbound traffic on a virtual interfaceof the processing environment, the monitoring is at a selected scope ofmonitoring, in which the selected scope includes an interface scope inwhich the virtual interface, as one entity, is monitored, or an addressscope in which a particular address of the virtual interface ismonitored. Based on the monitoring, a determination is made as towhether the virtual interface, as one entity, or the particular address,depending on the selected scope, has received an inbound frame but hasnot transmitted an outbound frame for the predefined amount of time.Based on determining that the inbound frame has been received but theoutbound frame has not been transmitted, a generated outbound frame isforwarded to cause address registration information for the virtualinterface to be refreshed.

The term “frame” as used herein includes any type of unit used tocommunicate and/or transmit data, including, but not limited to, forinstance, a frame, a packet, a unit of data, a unit of communicationand/or a unit of transmission.

As will be appreciated by one skilled in the art, aspects may beembodied as a system, method or computer program product. Accordingly,aspects may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “circuit,”“module” or “system”. Furthermore, aspects may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readablestorage medium. A computer readable storage medium may be, for example,but not limited to, an electronic, magnetic, optical, electromagnetic,infrared or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. More specific examples (a non-exhaustivelist) of the computer readable storage medium include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

Referring now to FIG. 8, in one example, a computer program product 800includes, for instance, one or more non-transitory computer readablestorage media 802 to store computer readable program code means or logic804 thereon to provide and facilitate one or more aspects of the presentinvention.

Program code embodied on a computer readable medium may be transmittedusing an appropriate medium, including but not limited to, wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programminglanguage, such as JAVA, Smalltalk, C++ or the like, and conventionalprocedural programming languages, such as the “C” programming language,assembler or similar programming languages. The program code may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider).

Aspects are described herein with reference to flowchart illustrationsand/or block diagrams of methods, apparatus (systems) and computerprogram products according to one or more embodiments. It will beunderstood that each block of the flowchart illustrations and/or blockdiagrams, and combinations of blocks in the flowchart illustrationsand/or block diagrams, can be implemented by computer programinstructions. These computer program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment, or portion of code, whichcomprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block may occurout of the order noted in the figures. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

In addition to the above, one or more aspects may be provided, offered,deployed, managed, serviced, etc. by a service provider who offersmanagement of customer environments. For instance, the service providercan create, maintain, support, etc. computer code and/or a computerinfrastructure that performs one or more aspects for one or morecustomers. In return, the service provider may receive payment from thecustomer under a subscription and/or fee agreement, as examples.Additionally or alternatively, the service provider may receive paymentfrom the sale of advertising content to one or more third parties.

In one aspect, an application may be deployed for performing one or moreaspects. As one example, the deploying of an application comprisesproviding computer infrastructure operable to perform one or moreaspects of the present invention.

As a further aspect, a computing infrastructure may be deployedcomprising integrating computer readable code into a computing system,in which the code in combination with the computing system is capable ofperforming one or more aspects.

As yet a further aspect, a process for integrating computinginfrastructure comprising integrating computer readable code into acomputer system may be provided. The computer system comprises acomputer readable medium, in which the computer medium comprises one ormore aspects. The code in combination with the computer system iscapable of performing one or more aspects.

Although various embodiments are described above, these are onlyexamples. For example, computing environments of other architectures canincorporate and use one or more aspects of the present invention.Additionally, the information provided in the various tables may differthan that described herein. Additionally, other scopes of monitoring oronly one scope of monitoring may be provided. If only one scope ofmonitoring is provided, that scope is the selected scope withoutrequiring any explicit action. Additionally, other timer and/or threadsleep values are possible. Further, the refresh primitive may includeadditional, less and/or different information. Many variations arepossible.

Further, other types of computing environments can benefit from one ormore aspects. As an example, an environment may include an emulator(e.g., software or other emulation mechanisms), in which a particulararchitecture (including, for instance, instruction execution,architected functions, such as address translation, and architectedregisters) or a subset thereof is emulated (e.g., on a native computersystem having a processor and memory). In such an environment, one ormore emulation functions of the emulator can implement one or moreaspects, even though a computer executing the emulator may have adifferent architecture than the capabilities being emulated. As oneexample, in emulation mode, the specific instruction or operation beingemulated is decoded, and an appropriate emulation function is built toimplement the individual instruction or operation.

In an emulation environment, a host computer includes, for instance, amemory to store instructions and data; an instruction fetch unit tofetch instructions from memory and to optionally, provide localbuffering for the fetched instruction; an instruction decode unit toreceive the fetched instructions and to determine the type ofinstructions that have been fetched; and an instruction execution unitto execute the instructions. Execution may include loading data into aregister from memory; storing data back to memory from a register; orperforming some type of arithmetic or logical operation, as determinedby the decode unit. In one example, each unit is implemented insoftware. For instance, the operations being performed by the units areimplemented as one or more subroutines within emulator software.

Further, a data processing system suitable for storing and/or executingprogram code is usable that includes at least one processor coupleddirectly or indirectly to memory elements through a system bus. Thememory elements include, for instance, local memory employed duringactual execution of the program code, bulk storage, and cache memorywhich provide temporary storage of at least some program code in orderto reduce the number of times code must be retrieved from bulk storageduring execution.

Input/Output or I/O devices (including, but not limited to, keyboards,displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives andother memory media, etc.) can be coupled to the system either directlyor through intervening I/O controllers. Network adapters may also becoupled to the system to enable the data processing system to becomecoupled to other data processing systems or remote printers or storagedevices through intervening private or public networks. Modems, cablemodems, and Ethernet cards are just a few of the available types ofnetwork adapters.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of one or more aspects of one or more aspectshas been presented for purposes of illustration and description, but isnot intended to be exhaustive or limited to the invention in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art without departing from the scope and spiritof one or more aspects. The embodiment was chosen and described in orderto best explain the principles of the one or more aspects and thepractical application, and to enable others of ordinary skill in the artto understand the one or more aspects for various embodiments withvarious modifications as are suited to the particular use contemplated.

What is claimed is:
 1. A computer program product for facilitatingcommunications within a processing environment, said computer programproduct comprising: a non-transitory computer readable storage mediumreadable by a processing circuit and storing instructions for executionby the processing circuit for performing a method comprising:monitoring, for a predefined amount of time, inbound traffic andoutbound traffic on a virtual interface of the processing environment;determining based on the monitoring whether for a selected component ofthe virtual interface an inbound frame has been received on the virtualinterface but no outbound frame has been transmitted on the virtualinterface to an external network device for the predefined amount oftime; and based on determining that the inbound frame has been receivedon the virtual interface but no outbound frame has been transmitted onthe virtual interface for the predefined amount of time, forwarding agenerated outbound frame to cause a refresh of address registrationinformation for the virtual interface to ensure that the addressregistration information is maintained.
 2. The computer program productof claim 1, wherein the selected component comprises an identifier ofthe virtual interface, in which the determining is based on monitoringinbound traffic and outbound traffic for the virtual interface, as oneentity.
 3. The computer program product of claim 1, wherein the selectedcomponent comprises a particular address of the virtual interface, inwhich the determining is based on monitoring inbound traffic andoutbound traffic for the particular address.
 4. The computer programproduct of claim 1, wherein the monitoring is performed at a selectedscope of monitoring, the selected scope comprising an interface scope inwhich inbound traffic and outbound traffic associated with a connectionidentifier of the virtual interface are monitored, the connectionidentifier being the selected component, and wherein the determiningcomprises determining whether the inbound frame has been received forthe connection identifier but no outbound frame has been transmitted forthe connection identifier, and the forwarding comprises forwarding thegenerated outbound frame based on determining the inbound frame has beenreceived but no outbound frame has been transmitted.
 5. The computerprogram product of claim 1, wherein the monitoring is performed at aselected scope of monitoring, the selected scope comprising an addressscope in which inbound traffic and outbound traffic on a particularaddress of the virtual interface are monitored, the particular addressbeing the selected component, and wherein the determining comprisesdetermining whether the inbound frame has been received for theparticular address but no outbound frame has been transmitted for theparticular address, and the forwarding comprises forwarding thegenerated outbound frame based on determining the inbound frame has beenreceived but no outbound frame has been transmitted.
 6. The computerprogram product of claim 1, wherein the address registration informationcomprises one or more Media Access Control (MAC) addresses stored in aforwarding table of a switch located within a network of the processingenvironment.
 7. The computer program product of claim 1, wherein themethod further comprises generating the generated outbound frame, thegenerating comprising creating a null gratuitous address resolutionprotocol (ARP) request frame, said null gratuitous ARP request framecomprising a destination address and a source address.
 8. The computerprogram product of claim 1, wherein the method further comprisesinitiating the determining based on a timer event, the timer eventindicating the predefined amount of time for monitoring has beenreached.
 9. The computer program product of claim 1, wherein themonitoring comprises recording a count of one or more inbound frames inan inbound counter and a count of one or more outbound frames, if any,in an outbound counter.
 10. The computer program product of claim 9,wherein the determining comprises checking the inbound counter and theoutbound counter.
 11. A computer system for facilitating communicationswithin a processing environment, said computer system comprising: amemory; and a processor in communications with the memory, wherein thecomputer system is configured to perform a method, said methodcomprising: monitoring, for a predefined amount of time, inbound trafficand outbound traffic on a virtual interface of the processingenvironment; determining based on the monitoring whether for a selectedcomponent of the virtual interface an inbound frame has been received onthe virtual interface but no outbound frame has been transmitted on thevirtual interface to an external network device for the predefinedamount of time; and based on determining that the inbound frame has beenreceived on the virtual interface but no outbound frame has beentransmitted on the virtual interface for the predefined amount of time,forwarding a generated outbound frame to cause a refresh of addressregistration information for the virtual interface to ensure that theaddress registration information is maintained.
 12. The computer systemof claim 11, wherein the selected component comprises an identifier ofthe virtual interface, in which the determining is based on monitoringinbound traffic and outbound traffic for the virtual interface, as oneentity.
 13. The computer system of claim 11, wherein the selectedcomponent comprises a particular address of the virtual interface, inwhich the determining is based on monitoring inbound traffic andoutbound traffic for the particular address.
 14. The computer system ofclaim 11, wherein the monitoring is performed at a selected scope ofmonitoring, the selected scope comprising an interface scope in whichinbound traffic and outbound traffic associated with a connectionidentifier of the virtual interface are monitored, the connectionidentifier being the selected component, and wherein the determiningcomprises determining whether the inbound frame has been received forthe connection identifier but no outbound frame has been transmitted forthe connection identifier, and the forwarding comprises forwarding thegenerated outbound frame based on determining the inbound frame has beenreceived but no outbound frame has been transmitted.
 15. The computersystem of claim 11, wherein the monitoring is performed at a selectedscope of monitoring, the selected scope comprising an address scope inwhich inbound traffic and outbound traffic on a particular address ofthe virtual interface are monitored, the particular address being theselected component, and wherein the determining comprises determiningwhether the inbound frame has been received for the particular addressbut no outbound frame has been transmitted for the particular address,and the forwarding comprises forwarding the generated outbound framebased on determining the inbound frame has been received but no outboundframe has been transmitted.
 16. The computer system of claim 11, whereinthe address registration information comprises one or more Media AccessControl (MAC) addresses stored in a forwarding table of a switch locatedwithin a network of the processing environment.
 17. The computer systemof claim 11, wherein the method further comprises generating thegenerated outbound frame, the generating comprising creating a nullgratuitous address resolution protocol (ARP) request frame, said nullgratuitous ARP request frame comprising a destination address and asource address.
 18. The computer system of claim 11, wherein the methodfurther comprises initiating the determining based on a timer event, thetimer event indicating the predefined amount of time for monitoring hasbeen reached.
 19. The computer system of claim 11, wherein themonitoring comprises recording a count of one or more inbound frames inan inbound counter and a count of one or more outbound frames, if any,in an outbound counter.
 20. The computer system of claim 19, wherein thedetermining comprises checking the inbound counter and the outboundcounter.